Method for making organic light emitting diode

ABSTRACT

A method for making an organic light emitting diode includes providing a preform structure including an anode electrode, a hole transport layer, and an organic light emitting layer stacked on each other in that order. The organic light emitting layer has a first surface and a second surface opposite to the first surface, and the second surface is in direct contact with the hole transport layer. A carbon nanotube structure is located on the first surface. A monomer solution is disposed on the carbon nanotube structure, and the monomer solution is formed by dispersing a monomer into an organic solvent. The monomer is polymerized to form a polymer, and a cathode electrode is formed on the polymer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. § 119 fromChina Patent Application No. 201710764605.1, filed on Aug. 30, 2017, inthe China Intellectual Property Office. This application is related tocommonly-assigned application entitled, “ORGANIC LIGHT EMITTING DIODE”,concurrently filed Ser. No. 15/851,889; “ORGANIC LIGHT EMITTING DIODE”,concurrently filed Ser. No. 15/848,315; “ORGANIC LIGHT EMITTING DIODE”,concurrently filed Ser. No. 15/848,334; “METHOD FOR MAKING ORGANIC LIGHTEMITTING DIODE”, concurrently filed Ser. No. 15/848,403; “METHOD FORMAKING ORGANIC LIGHT EMITTING DIODE”, concurrently filed Ser. No.15/851,896; “METHOD FOR MAKING ORGANIC LIGHT EMITTING DIODE”,concurrently filed Ser. No. 15/851,924. Disclosures of theabove-identified applications are incorporated herein by reference.

FIELD

The present application relates to organic light emitting diodes andmethods for making the same.

BACKGROUND

The organic light emitting diode (OLED) is a light emitting diodeincluding a light emitting layer composed of an organic compound. TheOLED has a light weight, thin thickness, multi-color, and lowmanufacturing cost. Thus, the OLED has been widely used in variousfields.

The carbon nanotube composite structure formed by carbon nanotubes andpolymer can be used as the electron transport layer of the OLED. Thecarbon nanotube composite structure can be formed by two methods. Onemethod includes dispersing the carbon nanotubes into an organic solventto form a carbon nanotube dispersion, mixing the carbon nanotubedispersion and a monomer solution, and polymerizing the monomer.However, the carbon nanotubes have poor dispersion in the organicsolvent, which affects the uniformity of the carbon nanotubes in thecomposite structure. Another method include completely melting thepolymer, and mixing the melted polymer and the carbon nanotubes.However, the carbon nanotubes have poor dispersion in the melted polymerbecause the melted polymer has greater viscosity. Thus, the uniformityof the carbon nanotubes in the composite structure is still poor. Whenthe carbon nanotube composite structure is used as the electrontransport layer of the OLED, the electron transport layer has poorability to transmit electrons.

What is needed, therefore, is to provide an organic light emitting diodeand a method for making the same that can overcome the above-describedshortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures, wherein:

FIG. 1 is a schematic process flow of a first embodiment of a method formaking a carbon nanotube composite structure.

FIG. 2 is a scanning electron microscope (SEM) image of a drawn carbonnanotube film.

FIG. 3 is an SEM image of a flocculated carbon nanotube film.

FIG. 4 is an SEM image of a pressed carbon nanotube film including aplurality of carbon nanotubes arranged along the same direction.

FIG. 5 is an SEM image of a pressed carbon nanotube film including aplurality of carbon nanotubes which is arranged along differentdirections.

FIG. 6 is an SEM image of a first composite structure surface of aCNT/PI composite structure.

FIG. 7 is an SEM image of the first composite structure surface of theCNT/PI composite structure coated with a gold film.

FIG. 8 is an atomic force microscope (AFM) image of the first compositestructure surface of the CNT/PI composite structure.

FIG. 9 is an AFM image of the first composite structure surface of theCNT/PI composite structure coated with a gold film.

FIG. 10 is a schematic process flow of a second embodiment of a methodfor making a carbon nanotube composite structure.

FIG. 11 is a schematic process flow of a third embodiment of a methodfor making a carbon nanotube composite structure.

FIG. 12 is a schematic process flow of a fourth embodiment of a methodfor making a carbon nanotube composite structure.

FIG. 13 is a schematic view of a fifth embodiment of an organic lightemitting diode.

FIG. 14 is a schematic process flow of a method for making the organiclight emitting diode of FIG. 13.

FIG. 15 is another schematic process flow of a method for making theorganic light emitting diode of FIG. 13.

FIG. 16 is yet another schematic process flow of a method for making theorganic light emitting diode of FIG. 13.

FIG. 17 is a schematic view of a sixth embodiment of an organic lightemitting diode.

FIG. 18 is a schematic process flow of a method for making the organiclight emitting diode of FIG. 17.

FIG. 19 is another schematic process flow of a method for making theorganic light emitting diode of FIG. 17.

FIG. 20 is yet another schematic process flow of a method for making theorganic light emitting diode of FIG. 17.

FIG. 21 is a schematic view of a seventh embodiment of an organic lightemitting diode.

FIG. 22 is another schematic view of the seventh embodiment of theorganic light emitting diode.

FIG. 23 is a schematic process flow of a method for making the organiclight emitting diode of FIG. 21.

FIG. 24 is another schematic process flow of a method for making theorganic light emitting diode of FIG. 21.

FIG. 25 is a schematic view of an eighth embodiment of an organic lightemitting diode.

FIG. 26 is a schematic process flow of a method for making the organiclight emitting diode of FIG. 25.

FIG. 27 is another schematic process flow of a method for making theorganic light emitting diode of FIG. 25.

FIG. 28 is a schematic view of a ninth embodiment of an organic lightemitting diode.

FIG. 29 is a schematic process flow of a method for making the organiclight emitting diode of FIG. 28.

FIG. 30 is another schematic process flow of a method for making theorganic light emitting diode of FIG. 28.

FIG. 31 is a schematic view of a tenth embodiment of an organic lightemitting diode.

FIG. 32 is a schematic process flow of a method for making the tenthembodiment of treating the carbon nanotube composite structure.

FIG. 33 is a schematic process flow of a method for making the organiclight emitting diode of FIG. 31.

FIG. 34 is another schematic process flow of a method for making theorganic light emitting diode of FIG. 31.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale, andthe proportions of certain parts may be exaggerated to illustratedetails and features better. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented.

The term “substantially” is defined to be essentially conforming to theparticular dimension, shape or other word that substantially modifies,such that the component need not be exact. For example, substantiallycylindrical means that the object resembles a cylinder, but can have oneor more deviations from a true cylinder. The term “comprising” means“including, but not necessarily limited to”; it specifically indicatesopen-ended inclusion or membership in a so-described combination, group,series and the like.

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

Referring to FIG. 1, a method for making a carbon nanotube compositestructure 130 of a first embodiment includes the following steps:

S1, placing a carbon nanotube structure 110 on a substrate surface 102of a substrate 100, wherein the carbon nanotube structure 110 has afirst surface 112 and a second surface 114 opposite to the first surface112, and the second surface 114 is in direct contact with the substratesurface 102;

S2, coating a monomer solution 140 on the carbon nanotube structure 110,wherein the monomer solution 140 is formed by dispersing a certainamount of monomers into an organic solvent;

S3, polymerizing the monomer; and

S4, removing the substrate 100.

In the step S1, the carbon nanotube structure 110 includes a pluralityof carbon nanotubes 118 uniformly distributed therein. A gap 116 isdefined between adjacent carbon nanotubes 118. The plurality of carbonnanotubes 118 is parallel to the first surface 112 and the secondsurface 114. The plurality of carbon nanotubes 118 is parallel to thesubstrate surface 102. The plurality of carbon nanotubes 118 can becombined by van der Waals attractive force. The carbon nanotubestructure 110 can be a substantially pure structure of the carbonnanotubes 118, with few impurities. The plurality of carbon nanotubes118 may be single-walled, double-walled, multi-walled carbon nanotubes,or their combinations. The carbon nanotubes 118 which are single-walledhave a diameter of about 0.5 nanometers (nm) to about 50 nm. The carbonnanotubes 118 which are double-walled have a diameter of about 1.0 nm toabout 50 nm. The carbon nanotubes 118 which are multi-walled have adiameter of about 1.5 nm to about 50 nm.

The plurality of carbon nanotubes 118 in the carbon nanotube structure110 can be orderly or disorderly arranged. The term ‘disordered carbonnanotube 118’ refers to the carbon nanotube structure 110 where thecarbon nanotubes 118 are arranged along many different directions, andthe aligning directions of the carbon nanotubes 118 are random. Thenumber of the carbon nanotubes 118 arranged along each differentdirection can be almost the same (e.g. uniformly disordered). The carbonnanotubes 118 can be entangled with each other. The term ‘ordered carbonnanotube 118’ refers to the carbon nanotube structure 110 where thecarbon nanotubes 118 are arranged in a consistently systematic manner,e.g., the carbon nanotubes 118 are arranged approximately along a samedirection and/or have two or more sections within each of which thecarbon nanotubes 118 are arranged approximately along a same direction(different sections can have different directions). The carbon nanotubestructure 110 can be a carbon nanotube layer structure including aplurality of drawn carbon nanotube films, a plurality of flocculatedcarbon nanotube films, or a plurality of pressed carbon nanotube films.

Referring to FIG. 2, the drawn carbon nanotube film includes a pluralityof successive and oriented carbon nanotubes 118 joined end-to-end by vander Waals attractive force therebetween. The carbon nanotubes 118 in thedrawn carbon nanotube film substantially extend along the samedirection. The carbon nanotubes are parallel to a surface of the drawncarbon nanotube film. The drawn carbon nanotube film is a free-standingfilm. The drawn carbon nanotube film can bend to desired shapes withoutbreaking. A film can be drawn from a carbon nanotube array to form thedrawn carbon nanotube film.

If the carbon nanotube structure 110 includes at least two stacked drawncarbon nanotube films, adjacent drawn carbon nanotube films can becombined by only the van der Waals attractive force therebetween.Additionally, when the carbon nanotubes 118 in the drawn carbon nanotubefilm are aligned along one preferred orientation, an angle can existbetween the orientations of carbon nanotubes 118 in adjacent drawncarbon nanotube films, whether stacked or adjacent. An angle between thealigned directions of the carbon nanotubes 118 in two adjacent drawncarbon nanotube films can be in a range from about 0 degree to about 90degrees. Stacking the drawn carbon nanotube films will improve themechanical strength of the carbon nanotube structure 110, furtherimproving the mechanical strength of the carbon nanotube compositestructure 130. In one embodiment, the carbon nanotube structure 110includes two layers of the drawn carbon nanotube films, and the anglebetween the aligned directions of the carbon nanotubes 118 in twoadjacent drawn carbon nanotube films is about 90 degrees.

Referring to FIG. 3, the flocculated carbon nanotube film includes aplurality of long, curved, disordered carbon nanotubes 118 entangledwith each other. The flocculated carbon nanotube film can be isotropic.The carbon nanotubes 118 can be substantially uniformly dispersed in theflocculated carbon nanotube film. Adjacent carbon nanotubes 118 areacted upon by van der Waals attractive force to obtain an entangledstructure. Due to the carbon nanotubes 118 in the flocculated carbonnanotube film being entangled with each other, the flocculated carbonnanotube film has excellent durability, and can be fashioned intodesired shapes with a low risk to the integrity of the flocculatedcarbon nanotube film. Further, the flocculated carbon nanotube film is afree-standing film.

Referring to FIGS. 4 and 5, the pressed carbon nanotube film includes aplurality of carbon nanotubes 118. The carbon nanotubes 118 in thepressed carbon nanotube film can be arranged along a same direction, asshown in FIG. 4. The carbon nanotubes 118 in the pressed carbon nanotubefilm can be arranged along different directions, as shown in FIG. 5. Thecarbon nanotubes 118 in the pressed carbon nanotube film can rest uponeach other. An angle between a primary alignment direction of the carbonnanotubes 118 and a surface of the pressed carbon nanotube film is about0 degree to approximately 15 degrees. The greater the pressure applied,the smaller the angle obtained. If the carbon nanotubes 118 in thepressed carbon nanotube film are arranged along different directions,the pressed carbon nanotube film can have properties that are identicalin all directions substantially parallel to the surface of the pressedcarbon nanotube film. Adjacent carbon nanotubes 118 are attracted toeach other and are joined by van der Waals attractive force. Therefore,the pressed carbon nanotube film is easy to bend to desired shapeswithout breaking. Further, the pressed carbon nanotube film is afree-standing film.

The term “free-standing” includes, but not limited to, the drawn carbonnanotube film, the flocculated carbon nanotube film, or the pressedcarbon nanotube film that does not have to be supported by a substrate.For example, the free-standing the drawn carbon nanotube film, theflocculated carbon nanotube film, or the pressed carbon nanotube filmcan sustain the weight of itself when it is hoisted by a portion thereofwithout any significant damage to its structural integrity. So, if thefree-standing the drawn carbon nanotube film, the flocculated carbonnanotube film, or the pressed carbon nanotube film is placed between twoseparate supporters, a portion of the free-standing the drawn carbonnanotube film, the flocculated carbon nanotube film, or the pressedcarbon nanotube film, not in contact with the two supporters, would besuspended between the two supporters and yet maintain film structuralintegrity.

The substrate surface 102 of the substrate 100 is very smooth. Theheight difference between the highest position of the substrate surface102 and the lowest position of the substrate surface 102 is nanoscale.The height difference between the highest position of the substratesurface 102 and the lowest position of the substrate surface 102 can bedefines as a smoothness of the substrate surface 102. The smoothness canbe greater than or equal to 0 nanometers and less than or equal to 30nanometers. The smoothness can be greater than or equal to 0 nanometersand less than or equal to 20 nanometers. The smoothness can also begreater than or equal to 0 nanometers and less than or equal to 10nanometers. The material of the substrate 100 can be sapphire,monocrystalline quartz, gallium nitride, gallium arsenide, silicon,graphene, or polymer. The melting point of the substrate 100 should begreater than the temperature of polymerizing the monomer. The length,width, and thickness of the substrate 100 are not limited. In oneembodiment, the substrate 100 is a silicon wafer.

Some organic solvent can be dripped on the first surface 112 of thecarbon nanotube structure 110. When the organic solvent is volatilized,the air between the carbon nanotube structure 110 and the substratesurface 102 can be removed under the surface tension of the organicsolvent. Thus, the carbon nanotube structure 110 can be tightly bondedto the substrate surface 102 of the substrate 100. The organic solventcan be ethanol, methanol, acetone, dichloroethane, or chloroform.

In the step S2, the monomer can be any monomer that can be polymerizedto form a polymer 120. The polymer 120 includes a phenolic resin (PF),an epoxy resin (EP), a polyurethane (PU), a polystyrene (PS), apolymethylmethacrylate (PMMA), a polycarbonate (PC), polyethyleneterephthalate (PET), phenylcyclobutene (BCB), polycycloolefin orpolyimide (PI), polyvinylidene fluoride (PVDF), and the like. In oneembodiment, the monomer is an imide, and the polymer 120 is a polyimide.The organic solvent includes ethanol, methanol, acetone, dichloroethaneor chloroform.

The monomer solution 140 has a small viscosity and good fluidity. Whenthe monomer solution 140 is coated on the first surface 112 of thesubstrate 100, the monomer solution 140 can pass through the gaps 116and contact with a part of the substrate surface 102. The first part ofthe substrate surface 102 is in direct contact with and coated by themonomer solution 140, the second part of the substrate surface 102 is indirect contact with the carbon nanotubes 118. The method for coating themonomer solution 140 is not limited and can be spin coating, injectioncoating, or the like. In one embodiment, the monomer solution 140 iscoated on the carbon nanotube structure 110 by spin coating.

In the step S3, the method for polymerizing the monomer is not limited,such as high temperature treatment. In one embodiment, the substrate 100and the carbon nanotube structure 110 coated with the monomer solution140 are placed in a reaction furnace. The reaction furnace is heated tothe temperature of polymerizing the monomer, and the monomer ispolymerized to form the polymer 120. The part surface of the carbonnanotube 118, that is directly contacted with the substrate surface 102of the substrate 100, is defined as a contact surface 117. Because thecarbon nanotubes 118 are tubular, the second surface 114 of the carbonnanotube structure 110 is in fact a ups and downs surface. The contactsurface 117 is parts of the second surface 114. Except for the contactsurface 117, the rest of second surface 114 is in direct contact withthe monomer solution 140. The gaps 116 are filled with the monomersolution 140. When the monomer is polymerized to form the solid polymer120, the polymer 120 is combined with the carbon nanotube structure 110to form the carbon nanotube composite structure 130.

In the step S4, the method for removing the carbon nanotube compositestructure 130 from the substrate surface 102 of the substrate 100 is notlimited. The carbon nanotube composite structure 130 can be peeled offfrom the substrate surface 102 of the substrate 100 by water immersion,blade, tape, or other tools.

The smoothness of the substrate surface 102 is nanoscale, thus thecontact surface 117 can be in direct contact with the substrate surface102 during coating the monomer solution 140 and polymerizing themonomer. Thus, there is no monomer solution 140 between the contactsurface 117 and the substrate surface 102 during coating the monomersolution 140 and polymerizing the monomer. Thus, when the carbonnanotube composite structure 130 is peeled from the substrate surface102, the contact surface 117 is exposed and not coated by the polymer120. A part outer wall of the carbon nanotubes 118, that is directlycontacted with the substrate surface 102, is exposed and not coated bythe polymer 120. Except for the contact surface 117, the rest of theouter walls of carbon nanotubes 118 are coated by and in direct contactwith the polymer 120.

The carbon nanotube composite structure 130 includes the plurality ofcarbon nanotubes 118 and the polymer 120. The plurality of carbonnanotubes 118 are uniformly dispersed in the polymer 120. The pluralityof carbon nanotubes 118 can be joined end-to-end and extend along thesame direction. The plurality of carbon nanotubes 118 can also extendalong different directions, or entangled with each other to form anetwork-like structure. The carbon nanotube composite structure 130 hasa first composite structure surface 132. The first composite structuresurface 132 is in direct contact with the substrate surface 102 beforepeeling the carbon nanotube composite structure 130 off from thesubstrate 100. The length direction of the plurality of carbon nanotubes118 is parallel to the first composite structure surface 132. Thesurface of the polymer 120 near the substrate 100 is defined as a lowersurface 122. The contact surface 117 and the lower surface 122 togetherform the first composite structure surface 132. Thus, the contactsurface 117 is a part of the first composite structure surface 132 andexposed from the polymer 120. The contact surface 117 is an exposedsurface and can protrude out of the lower surface 122 of the polymer120. The height difference between the exposed surface and the lowersurface 122 of the polymer 120 is nanoscale. Since the smoothness of thesubstrate surface 102 is at nanoscale level, the first compositestructure surface 132 is also smooth at nanoscale level. The heightdifference between the contact surface 117 and the lower surface 122 canbe greater than or equal to 0 nanometers and less than or equal to 30nanometers. The height difference between the contact surface 117 andthe lower surface 122 can be greater than or equal to 0 nanometers andless than or equal to 20 nanometers. The height difference between thecontact surface 117 and the lower surface 122 can also be greater thanor equal to 0 nanometers and less than or equal to 10 nanometers.

In one embodiment, the polymer 120 is polyimide, the carbon nanotubestructure 110 is two stacked drawn carbon nanotube films, and the anglebetween the aligned directions of the carbon nanotubes 118 in twoadjacent drawn carbon nanotube films is about 90 degrees.

In one embodiment, to synthesize poly(amic acid) (PAA) solution, 2.0024g of ODA (10 mmol) was placed in a three-neck flask containing 30.68 mLof anhydrous DMAc under nitrogen purge at room temperature. After ODA iscompleted dissolved in DMAc, 2.1812 g of PMDA (10 mmol) is added in oneportion. Thus, the solid content of the solution is about 12%. Themixture is stirred at room temperature under nitrogen purge for 12 h toproduce a PAA solution. The two stacked drawn carbon nanotube films arelocated on a silicon wafer, wherein the angle between the aligneddirections of the carbon nanotubes 118 in two adjacent drawn carbonnanotube films is about 90 degrees. Then the PAA solution is coated onthe two stacked drawn carbon nanotube films, and the PAA solution willgradually penetrate into the two stacked drawn carbon nanotube films toform a preform. The preform is thermal imidized in muffle furnace at 80°C., 120° C., 180° C., 300° C., and 350° C. for 1 h respectively to forma CNT/PI composite structure. Finally, the CNT/PI composite structure ispeeled off from the silicon wafer.

FIG. 6 is an SEM image of the first composite structure surface of aCNT/PI composite structure. As shown in FIG. 6, the carbon nanotubes 118are uniformly dispersed in the CNT/PI composite structure.

FIG. 7 is an SEM image of the first composite structure surface of theCNT/PI composite structure coated with a gold film, and the thickness ofthe gold film is about 1 nm. As shown in FIG. 7, the first compositestructure surface 132 is a smooth surface with no ups and downs from thenaked eye. The height difference between the highest place of the firstcomposite structure surface 132 and the lowest place of the firstcomposite structure surface 132 is nanoscale. FIG. 8 is an atomic forcemicroscope (AFM) image of the first composite structure surface of theCNT/PI composite structure. FIG. 9 is an AFM image of the firstcomposite structure surface of the CNT/PI composite structure coatedwith a gold film, and the thickness of the gold film is about 3 nm. Asshown in FIG. 8 and FIG. 9, it is also find that the first compositestructure surface 132 is a smooth surface.

Referring to FIG. 10, a method for making a carbon nanotube compositestructure 160 of a second embodiment includes the following steps:

S21, placing the carbon nanotube structure 110 on the substrate surface102 of the substrate 100, wherein the carbon nanotube structure 110 hasthe first surface 112 and the second surface 114 opposite to the firstsurface 112, and the second surface 114 is in direct contact with thesubstrate surface 102;

S22, locating a graphene layer 150 on the first surface 112;

S23, coating a monomer solution 140 on the graphene layer 150 and thecarbon nanotube structure 110, wherein the monomer solution 140 isformed by dispersing the monomer into the organic solvent;

S24, polymerizing the monomer; and

S25, removing the substrate 100.

In this embodiment, the method for making the carbon nanotube compositestructure 160 is similar to the method for making the carbon nanotubecomposite structure 130 above except that the graphene layer 150 islocated on the first surface 112 before coating the monomer solution140.

The graphene layer 150 is a two dimensional film structure. If thegraphene layer 150 includes a plurality of graphene films, the pluralityof graphene films can overlap each other to form a large area. Thegraphene film is a one-atom thick planar sheet composed of a pluralityof sp²-bonded carbon atoms. The graphene layer 150 can be afree-standing structure. The term “free-standing structure” means thatthe graphene layer 150 can sustain the weight of itself when it ishoisted by a portion thereof without any significant damage to itsstructural integrity. So, if the graphene layer 150 is placed betweentwo separate supports, a portion of the graphene layer 150 not incontact with the two supports, would be suspended between the twosupports and yet maintain structural integrity. When the plurality ofgraphene films overlap each other, a gap is formed between adjacent twographene films. During coating the monomer solution 140, the monomersolution 140 can pass through the graphene layer 150 and the carbonnanotube structure 110 to arrive at the substrate surface 102, becauseboth the graphene layer 150 and the carbon nanotube structure 110 havegaps 106.

Referring to FIG. 11, a method for making a carbon nanotube compositestructure 170 of a third embodiment includes the following steps:

S31, placing the carbon nanotube structure 110 on the substrate surface102 of the substrate 100 to form a preform structure 172, wherein thecarbon nanotube structure 110 has the first surface 112 and the secondsurface 114 opposite to the first surface 112, and the second surface114 is in direct contact with the substrate surface 102;

S32, locating two preform structures 172 on a base 174, wherein the twopreform structures 172 are spaced apart from each other, the substrates100 of the two preform structures 172 and the base 174 form a mold 176having an opening, and the carbon nanotube structures 110 of the twopreform structures 172 are opposite to each other and inside of the mold176;

S33, injecting the monomer solution 140 into the inside of the mold 176from the opening of the mold 176, wherein the monomer solution 140 isformed by dispersing the monomer into the organic solvent;

S34, polymerizing the monomer; and

S35, removing the substrates 100 and the base 174.

In this embodiment, the method for making the carbon nanotube compositestructure 170 is similar to the method for making the carbon nanotubecomposite structure 130 above except the steps S32 and S33.

In the step S32, the method for making the mold 176 is not limited. Forexample, the two preforms structures 172 and the base 174 are fixedtogether by sticking or mechanically fastening to form the mold 176. Inone embodiment, the two preforms structures 172 and the base 174 arefixed by a sealant, and the sealant is 706B vulcanized silicon rubber.The opening is on the top of the mold 176. The carbon nanotube structure110 of each of the two preforms structures 172 is located inside of themold 176. The substrate 100 of each of the two preforms structures 172forms the sidewall of the mold 176. The material of the base 174 is notlimited, such as glass, silica, metal or metal oxide. In one embodiment,the material of the substrate 174 is glass. The carbon nanotubestructure 110 in the mold 176 would not fall off from the substrate 100because the carbon nanotube structure 110 itself has viscosity. Theorganic solvent can be dripped so that the carbon nanotube structure 110is firmly adhered to the substrate 100.

Furthermore, the length or width of the carbon nanotube structure 110can be greater than the length or width of the substrate surface 102.When the carbon nanotube structure 110 is disposed on the substratesurface 102, the excess carbon nanotube structure 110 can be folded intothe back surface of the substrate 100, and an adhesive can be applied tothe back surface of the substrate 100. Thus, the carbon nanotubestructure 110 in the mold 176 is firmly adhered to the substrate 100 andwould not fall off from the substrate 100. The back surface is oppositeto the substrate surface 102, and the substrate surface 102 can beconsidered the front surface. The melting point of the adhesive needs tobe greater than the temperature of polymerizing the monomer.

In the step S33, the monomer solution 140 is slowly injected into theinside of the mold 176 along the inner wall of the mold 176. The monomersolution 140 completely submerges the carbon nanotube structure 110. Themonomer solution 140 would not break the integrity of the carbonnanotube structure 110 during injecting the monomer solution 140 becausethe carbon nanotube structure 110 is supported by the substrate 100.

Referring to FIG. 12, a method for making a carbon nanotube compositestructure 180 of a fourth embodiment includes the following steps:

S41, placing the carbon nanotube structure 110 on the substrate surface102 of the substrate 100, wherein the carbon nanotube structure 110 hasthe first surface 112 and the second surface 114 opposite to the firstsurface 112, and the second surface 114 is in direct contact with thesubstrate surface 102;

S42, placing the carbon nanotube structure 110 and the substrate 100into a container 182, wherein the container 182 has an opening;

S43, injecting the monomer solution 140 into the container 182 from theopening of the container 182, wherein the monomer solution 140 is formedby dispersing the monomer into the organic solvent;

S44, polymerizing the monomer; and

S45, removing the substrates 100 and the container 182.

In this embodiment, the method for making the carbon nanotube compositestructure 180 is similar to the method for making the carbon nanotubecomposite structure 130 above except the steps S42 and S43.

In the step S42, the container 182 has a bottom. When the carbonnanotube structure 110 and the substrate 100 are located in thecontainer 182, the substrate 100 is located on and in direct contactwith the bottom of the container 182. The carbon nanotube structure 110spaced apart from the bottom by the substrate 100. The material of thecontainer 182 is not limited, such as silica, metal, glass, or metaloxide. In one embodiment, the material of the container 182 is glass.

In the step S43, the monomer solution 140 does not break the integrityof the carbon nanotube structure 110 during injecting the monomersolution 140 because the carbon nanotube structure 110 is supported bythe substrate 100. The amount of the monomer solution 140 can beadjusted so that the monomer solution 140 submerges the entire carbonnanotube structure 110, or submerges only a part of the carbon nanotubestructure 110. When the monomer solution 140 submerges only a part ofthe carbon nanotube structure 110, the thickness of the polymer 120 isless than the thickness of the carbon nanotube structure 110. Thus, inthe carbon nanotube composite structure 180, some carbon nanotubes 118are located in and completely coated by the polymer 120, and some carbonnanotubes 118 are exposed from and extend out of the polymer 120. In oneembodiment, the carbon nanotube structure 110 includes three stackeddrawn carbon nanotube films, and the monomer solution 140 submerges onlya part of the carbon nanotube structure 110. In the carbon nanotubecomposite structure 180, the first drawn carbon nanotube film, thesecond drawn carbon nanotube film and the third drawn carbon nanotubefilm are stacked. The second drawn carbon nanotube film is between thefirst drawn carbon nanotube film and the third drawn carbon nanotubefilm. The entire outer walls of the carbon nanotubes 118 in the seconddrawn carbon nanotube film are coated by the polymer 120. Partial outerwall of the carbon nanotubes 118 in the first drawn carbon nanotube filmare exposed. The contact surfaces 117 of the carbon nanotubes 118 in thethird drawn carbon nanotube film are exposed.

The monomer solution 140 has a smaller viscosity than the moltenpolymer, thus after coating the monomer solution 140 and polymerizingthe monomer, the carbon nanotubes 118 can uniformly dispersed in thepolymer 120. In above methods, the substrate 100 has a nanoscale smoothsubstrate surface 102, thus some carbon nanotubes of the carbon nanotubecomposites 130, 160, 170, and 180 are exposed from the polymer 120,improving the conductivity of the carbon nanotube composites 130, 160,170, and 180.

The carbon nanotube composite structures 130, 170, and 180 can be usedas an electron transport layer in an organic light emitting diode(OLED). The OLEDs and the methods for making the OLEDs are described indetail below.

Referring to FIG. 13, an OLED 10 of a fifth embodiment includes asupport body 11, an anode electrode 12, a hole transport layer 13, anorganic light emitting layer 14, the carbon nanotube composite structure130, and a cathode electrode 15. The support body 11, the anodeelectrode 12, the hole transport layer 13, the organic light emittinglayer 14, the carbon nanotube composite structure 130, and the cathodeelectrode 15 are stacked on each other in that order. The carbonnanotube composite structure 130 includes the plurality of carbonnanotubes 118 and the polymer 120, and the plurality of carbon nanotubes118 is dispersed in the polymer 120. The contact surface 117 of theplurality of carbon nanotubes 118 is in direct contact with the organiclight emitting layer 14. The rest surfaces of the plurality of carbonnanotubes 118 are covered by and in direct contact with the polymer 120.The carbon nanotube composite structure 130 serves as the electrodetransport layer for transporting electrons. In the fifth embodiment, thematerial of the polymer 120 can transport electrons and is an aromaticcompound having a large conjugated plane, such as 8-Hydroxyquinolinealuminum salt (AlQ), 2-(4-tert(4-biphenyl)-1,3,4-oxadiazole (PBD), Beq₂or 4,4′-Bis(2,2-diphenylvinyl)-1,1′-biphenyl (DPVBi).

The support body 11 can be transparent or opaque. The material of thesupport body 11 can be glass, quartz, transparent plastic or resin. Inthe fifth embodiment, the support body 11 is a glass plate. The anodeelectrode 12 is a transparent conductive layer or a porous meshstructure, such as ITO layer, FTO layer, or the like. In the fifthembodiment, the material of the anode electrode 12 is ITO.

The hole transport layer 13 has a strong hole transporting ability. Thematerial of the hole transport layer 13 can beN,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,4-diamine (NPB),N,N′-diphenyl-N,N′-bis(m-methylphenyl)-1, Biphenyl-4,4′-diamine (TPD),or 4,4′,4″-tris(3-methylphenylaniline) triphenylamine (MTDATA). In thefifth embodiment, the material of the hole transport layer 13 is NPB.

The organic light emitting layer 14 is a polymer or a small moleculeorganic compound having high quantum efficiency, good semiconductivity,and thermal stability. A molecular weight of the polymer can be in arange from about 10000 to about 100000. The polymer can be a conductiveconjugated polymer or a semiconductor conjugated polymer. A molecularweight of the small molecule organic compound can be in a range fromabout 500 to about 20000. The small molecule organic compound can be anorganic dye. The organic dye has characteristics of strong chemicalmodification, wide selection range, easy purification and high quantumefficiency. The small molecule organic compound can be a red, green, orblue material. When the small molecule organic compound is a redmaterial, the red material can be selected from the group consisting ofrhodamine dyes, DCM, DCT, DCJT, DCJTB, DCJTI and TPBD. When the smallmolecule organic compound is a green material, the green material can beselected from coumarin 6, quinacridone (QA), coronene, naphthalimide.When the small molecule organic compound is a blue material, the bluematerial can be selected from the group consisting ofN-arylbenzimidazoles, and 1,2,4-triazole derivatives (TAZ) anddistyrylarylene. In the fifth embodiment, the material of the organiclight emitting layer 14 is Alq3. The cathode electrode 15 is atransparent layer, an opaque conductive layer, or a porous meshstructure, such as a metal thin film, a metal mesh, an ITO layer, an FTOlayer, and the like. In the fifth embodiment, the cathode electrode 15is an aluminum layer.

The OLED 10 can further include a hole injection layer (not shown infigure) and an electron injection layer (not shown in figure). The holeinjection layer is between the anode electrode 12 and the hole transportlayer 13. The electron injection layer is between the carbon nanotubecomposite structure 130 and the cathode electrode 15. The material ofthe hole injection layer can be copper phthalocyanine (CuPc) or PEDOT:PSS. The PEDOT is a polymerization of 3,4-ethylenedioxythiophene monomer(EDOT). The PSS is polystyrene sulfonate. The material of the electroninjecting layer is an alkali metal or an alkali metal compound having alow work function, such as lithium fluoride (LiF), calcium (Ca), ormagnesium (Mg).

The carbon nanotube composite structure 130 can conduct and transportelectrons, so the cathode electrode 15 can be omitted. When the cathodeelectrode 15 is omitted, the carbon nanotube composite structure 130 isused as both the electron transport layer and the cathode electrode. Inthe OLED 10 as shown in FIG. 13, the plurality of carbon nanotubes 118substantially extend along the same direction and are uniformlydispersed in the polymer 120, thus the transmitting electrons ability ofthe electron transport layer is enhanced.

Referring to FIG. 14, a method for making the OLED 10 of the fifthembodiment includes the following steps:

S51, providing a preform structure 16 including the support body 11, theanode electrode 12, the hole transport layer 13, and the organic lightemitting layer 14, wherein the support body 11, the anode electrode 12,the hole transport layer 13, and the organic light emitting layer 14 arestacked on each other in that order;

S52, placing the carbon nanotube structure 110 on the preform structure16, wherein the carbon nanotube structure 110 is in direct contact withthe surface of the organic light emitting layer 14 away from the holetransport layer 13;

S53, applying the monomer solution 140 to the carbon nanotube structure110;

S54, polymerizing the monomer to form the polymer 120; and

S55, forming the cathode electrode 15 on the surface of the polymer 120away from the preform structure 16.

In the step S51, the method for sequentially stacking the support body11, the anode electrode 12, the hole transport layer 13, and the organiclight emitting layer 14 is not limited, such as sputtering, coating,vapor deposition, mask etching, spraying, or inkjet printing. The stepsS52 to S54 are similar to the steps S1 to S3 of the first embodiment. Inorder to ensure that the support body 11, the anode electrode 12, thehole transport layer 13, and the organic light emitting layer 14 wouldnot be damaged by the temperature of polymerizing the monomer, themelting points of the support body 11, the anode electrode 12, the holetransport layer 13, and the organic light emitting layer 14 should begreater than the temperature of polymerizing the monomer. In the stepS55, the cathode electrode 15 is formed by a conventional method, suchas sputtering, coating, vapor deposition or the like. It is to beunderstood that the step 55 can be omitted when the cathode electrode 15is omitted from the OLED 10 and the carbon nanotube composite structure130 is used as both the electron transport layer and the electrode.

Referring to FIG. 15, another method for making the OLED 10 of the fifthembodiment includes the following steps:

S51′, providing the preform structure 16 including the support body 11,the anode electrode 12, the hole transport layer 13, and the organiclight emitting layer 14, wherein the support body 11, the anodeelectrode 12, the hole transport layer 13, and the organic lightemitting layer 14 are stacked on each other in that order;

S52′, placing the carbon nanotube composite structure 130 on the surfaceof the organic light emitting layer 14 away from the hole transportlayer 13, wherein the first composite structure surface 132 of thecarbon nanotube composite structure 130 is in direct contact with theorganic light emitting layer 14; and

S53′, forming the cathode electrode 15 on the surface of the carbonnanotube composite structure 130 away from the organic light emittinglayer 14.

In this embodiment, the anode electrode 12, the hole transport layer 13,the organic light emitting layer 14, the carbon nanotube compositestructure 130, and the cathode electrode 15 are stacked on each other inthat order on the support body 11.

In the step S52′, in order to make the carbon nanotube compositestructure 130 and the organic light emitting layer 14 to be combinedfirmly, the carbon nanotube composite structure 130 and the organiclight emitting layer 14 can be hot pressed or cold pressed beforeforming the cathode electrode 15. In one embodiment, the carbon nanotubecomposite structure 130 is placed on the organic light emitting layer 14to form a whole structure; the whole structure is located in a hot-pressapparatus having a metal roll and a heating element. The heated metalroll presses the whole structure, the polymer 120 and the organic lightemitting layer 14 are softened, and the air between the organic lightemitting layer 14 and the carbon nanotube composite structure 130 isexhausted, so that the organic light emitting layer 14 and the carbonnanotube composite structure 130 are tightly pressed together. Duringpressing by the metal roll, the pressure from the metal roll is in arange from about 5 kg to about 20 kg. The temperature of the metal rollshould not cause the organic light emitting layer 14 and the carbonnanotube composite structure 130 to melt. It is to be understood thatthe step 53′ can be omitted when the cathode electrode 15 is omittedfrom the OLED 10 and the carbon nanotube composite structure 130 is usedas both the electron transport layer and the electrode.

Referring to FIG. 16, yet another method for making the OLED 10 of thefifth embodiment includes the following steps:

S51″, providing the carbon nanotube composite structure 130, wherein thecarbon nanotube composite structure 130 has the first compositestructure surface 132 and a second composite structure surface 138opposite to the first composite structure surface 132;

S52″, forming the cathode electrode 15 on the second composite structuresurface 138, wherein the plurality of carbon nanotubes 118 of the carbonnanotube composite structure 130 is spaced apart from the cathodeelectrode 15; and

S53″, forming the preform structure 16 on the first composite structuresurface 132, wherein the plurality of carbon nanotubes 118 is in directcontact with the organic light emitting layer 14.

In this embodiment, the method for making the OLED 10 is shown where thecathode electrode 15 is formed on the second composite structure surface138 of the carbon nanotube composite structure 130, and the preformstructure 16 is formed on the first composite structure surface 132 ofthe carbon nanotube composite structure 130. In this embodiment,firstly, the organic light emitting layer 14 is formed on the firstcomposite structure surface 132, then the hole transport layer 13 isformed on the surface of the organic light emitting layer 14 away fromthe first composite structure surface 132; secondly, the anode electrode12 is formed on the surface of the hole transport layer 13 away from theorganic light emitting layer 14, then the support body 11 is placed onthe surface of the anode electrode 12 away from the hole transport layer13. The method for forming the anode electrode 12, the hole transportlayer 13, or the organic light emitting layer 14 can be sputtering,coating, vapor deposition, mask etching, spraying, or inkjet printing.The step S2″ can be omitted when the cathode electrode 15 is omittedfrom the OLED 10 and the carbon nanotube composite structure 130 is usedas both the electron transport layer and the electrode. The carbonnanotube composite structure 130 is a free-standing structure and cansupport other elements in the OLED 10, thus support body 11 of thepreform structure 16 can be omitted.

Referring to FIG. 17, an OLED 20 of a sixth embodiment is shown. TheOLED 20 is similar to the OLED 10 above except that the first compositestructure surface 132 is in direct contact with the organic lightemitting layer 14 in the OLED 10, and the first composite structuresurface 132 is spaced apart from the organic light emitting layer 14 inthe OLED 20.

Referring to FIG. 18, a method for making the OLED 20 of the sixthembodiment includes the following steps:

S61, placing the carbon nanotube structure 110 on the cathode electrode15;

S62, applying the monomer solution 140 to the carbon nanotube structure110;

S63, polymerizing the monomer to form the polymer 120; and

S64, forming the preform structure 16 on the surface of the polymer 120away from the cathode electrode 15, wherein the polymer 120 is in directcontact with the organic light emitting layer 14, and the carbonnanotube structure 110 is spaced apart from the organic light emittinglayer 14.

In order to ensure that the cathode electrode 15 would not be damaged bythe temperature of polymerizing the monomer, the melting points of thecathode electrode 15 should be greater than the temperature ofpolymerizing the monomer. In this embodiment, the steps of applying themonomer solution 140 to the carbon nanotube structure 110 andpolymerizing the monomer are similar to the steps S2 and S3 of the firstembodiment.

Referring to FIG. 19, another method for making the OLED 20 of the sixthembodiment includes the following steps:

S61′, providing the preform structure 16 including the support body 11,the anode electrode 12, the hole transport layer 13, and the organiclight emitting layer 14, wherein the support body 11, the anodeelectrode 12, the hole transport layer 13, and the organic lightemitting layer 14 are stacked on each other in that order;

S62′, placing the carbon nanotube composite structure 130 on the surfaceof the organic light emitting layer 14 away from the hole transportlayer 13, wherein the first composite structure surface 132 of thecarbon nanotube composite structure 130 is spaced apart from the organiclight emitting layer 14; and

S63′, forming the cathode electrode 15 on the first composite structuresurface 132.

The method as shown in FIG. 19 is similar to the method as shown in FIG.15 above except that the first composite structure surface 132 is indirect contact with the organic light emitting layer 14 in the method asshown in FIG. 15, and the first composite structure surface 132 isspaced apart from the organic light emitting layer 14 in the method asshown in FIG. 19.

Referring to FIG. 20, yet another method for making the OLED 20 of thesixth embodiment includes the following steps:

S61″, providing the carbon nanotube composite structure 130, wherein thecarbon nanotube composite structure 130 has the first compositestructure surface 132 and the second composite structure surface 138opposite to the first composite structure surface 132;

S62″, forming the cathode electrode 15 on the first composite structuresurface 132, wherein the plurality of carbon nanotubes 118 is in directcontact with the cathode electrode 15; and

S63″, forming the preform structure 16 on the second composite structuresurface 138, wherein organic light emitting layer 14 is in directcontact with the second composite structure surface 138, and theplurality of carbon nanotubes 118 of the carbon nanotube compositestructure 130 is spaced apart from the organic light emitting layer 14.

The method as shown in FIG. 20 is similar to the method as shown in FIG.16 above except that the first composite structure surface 132 is indirect contact with the organic light emitting layer 14 in the method asshown in FIG. 16, and the first composite structure surface 132 isspaced apart from the organic light emitting layer 14 in the method asshown in FIG. 20.

Referring to FIG. 21, an OLED 30 of a seventh embodiment is shown. TheOLED 30 is similar to the OLED 10 above except that the carbon nanotubecomposite structure 170 is used as the electron transport layer of theOLED 30. The carbon nanotube composite structure 170 includes aplurality of first carbon nanotubes 1180 and a plurality of secondcarbon nanotubes 1182. The plurality of second carbon nanotubes 1182 andthe plurality of first carbon nanotubes 1180 are dispersed in thepolymer 120. Partial surface of each first carbon nanotube 1180 isexposed from the polymer 120 and in direct contact with the organiclight emitting layer 14. Partial surface of each second carbon nanotube1182 is exposed from the polymer 120 and in direct contact with thecathode electrode 15. The plurality of second carbon nanotubes 1182 andthe plurality of first carbon nanotubes 1180 can be spaced apart fromeach other, as shown in FIG. 21. The plurality of second carbonnanotubes 1182 and the plurality of first carbon nanotubes 1180 can alsobe in direct contact with each other, as shown in FIG. 22. Whenplurality of second carbon nanotubes 1182 and the plurality of firstcarbon nanotubes 1180 are in direct contact with each other, thematerial of the polymer 120 is not limited and can be insulated.

Referring to FIG. 23, a method for making the OLED 30 of the seventhembodiment includes the following steps:

S71, placing the carbon nanotube structure 110 on the preform structure16 to form a first composite structure 173, wherein the carbon nanotubestructure 110 is in direct contact with the surface of the organic lightemitting layer 14 away from the hole transport layer 13;

S72, placing the other carbon nanotube structure 110 on the cathodeelectrode 15 to form a second composite structure 175;

S73, locating the first composite structure 173 and the second compositestructure 175 on the base 174, wherein the first composite structure 173and the second composite structure 175 are spaced apart from each other;the base 174, the preform structure 16, and the cathode electrode 15form a second mold 177 having an opening; and the carbon nanotubestructures 110 of the first composite structure 173 and the secondcomposite structure 175 are opposite to each other and inside of thesecond mold 177;

S74, injecting the monomer solution 140 into the inside of the secondmold 177 from the opening, wherein the monomer solution 140 is formed bydispersing the monomer into the organic solvent;

S75, polymerizing the monomer; and

S76, removing the base 174.

The method for making the OLED 30 as shown in FIG. 23 is similar to themethod for making the carbon nanotube composite structure 170 as shownin FIG. 11 above except that: 1) in FIG. 11, the carbon nanotubestructure 110 is placed on the substrate 100 to form the preformstructure 172, the substrates 100 of two preform structures 172 and thebase 174 form the mold 176; in FIG. 23, the carbon nanotube structure110 is placed on the preform structure 16 to form the first compositestructure 173, another carbon nanotube structure 110 is placed on thecathode electrode 15 to form the second composite structure 175, and thebase 174, the preform structure 16, and the cathode electrode 15 formthe second mold 177; 2) in FIG. 11, all of the base 174 and the twosubstrates 100 are removed; in FIG. 23, only the base 174 is removed.

Referring to FIG. 24, another method for making the OLED 30 of theseventh embodiment includes the following steps:

S71′, providing the preform structure 16 including the support body 11,the anode electrode 12, the hole transport layer 13, and the organiclight emitting layer 14, wherein the support body 11, the anodeelectrode 12, the hole transport layer 13, and the organic lightemitting layer 14 are stacked on each other in that order;

S72′, placing the carbon nanotube composite structure 170 on the surfaceof the organic light emitting layer 14 away from the hole transportlayer 13, wherein carbon nanotube composite structure 170 includes theplurality of first carbon nanotubes 1180 and the plurality of secondcarbon nanotubes 1182, the part of the surface of each first carbonnanotube 1180 is exposed from the polymer 120 and in direct contact withthe organic light emitting layer 14, and the part of the surface of eachsecond carbon nanotube 1182 is exposed from the polymer 120; and

S73′, forming the cathode electrode 15 on the surface of the carbonnanotube composite structure 170 away from the organic light emittinglayer 14, wherein the part of the surface of each second carbon nanotube1182 is exposed from the polymer 120 and in direct contact with thecathode electrode 15.

The method as shown in FIG. 24 is similar to the method as shown in FIG.19 above except that the carbon nanotube composite structure isdifferent in the two methods.

Yet another method for making the OLED 30 of the seventh embodimentincludes the following steps:

S71″, providing the carbon nanotube composite structure 170 including athird surface and a fourth surface opposite to the third surface;

S72″, forming the cathode electrode 15 on the third surface; and

S73″, placing the preform structure 16 on the fourth surface, whereinthe organic light emitting layer 14 is in direct contact with the fourthsurface.

This method is similar to the method as shown in FIG. 20 above exceptthat the carbon nanotube composite structure is different in the twomethods. This method and the methods shown in FIGS. 16 and 20 have someadvantages below. The parts of surface of the carbon nanotubes 118 areexposed from the polymer 120 before forming the cathode electrode 15 (orthe organic light emitting layer 14). When the cathode electrode 15 (orthe organic light emitting layer 14) is formed by sputtering, coating,vapor deposition, the exposed surface of the carbon nanotubes 118 arecompletely covered by the cathode electrode 15 (or the organic lightemitting layer 14). Thus, the cathode electrode 15 (or the organic lightemitting layer 14) has a large contact area with the carbon nanotubes118, enhancing the ability of the carbon nanotubes 118 to transmitelectrons.

Referring to FIG. 25, an OLED 40 of an eighth embodiment is shown. TheOLED 40 is similar to the OLED 30 above except that the carbon nanotubecomposite structure 180 is used as the electron transport layer of theOLED 40. The carbon nanotube composite structure 180 further includes aplurality of third carbon nanotubes 1184 dispersed in the polymer 120.Entire surface of the plurality of third carbon nanotubes 1184 is indirect contact with the polymer 120. The plurality of first carbonnanotubes 1180, the plurality of second carbon nanotubes 1182, and theplurality of third carbon nanotubes 1184 are in direct contact with eachother in the thickness direction of the carbon nanotube compositestructure 180. Thus, the electrons can be transferred from the cathodeelectrode 15 to the organic light emitting layer 14. Thus, the carbonnanotube composite structure 180 can be used as the electron transportlayer for transporting electrons no matter the material of the polymer120 can or cannot transmit electrons. Thus, the material of the polymeris not limited.

Referring to FIG. 26, a method for making the OLED 40 of the eighthembodiment includes the following steps:

S81, placing the carbon nanotube structure 110 on the preform structure16, wherein the carbon nanotube structure 110 is in direct contact withthe surface of the organic light emitting layer 14 away from the holetransport layer 13;

S82, placing the carbon nanotube structure 110 and the preform structure16 into the container 182, wherein the container 182 has the opening;

S83, injecting the monomer solution 140 into the container 182 from theopening of the container 182, wherein the monomer solution 140 is formedby dispersing the monomer into the organic solvent;

S84, polymerizing the monomer to form the polymer 120;

S85, removing the container 182; and

S86, forming the cathode electrode 15 on the surface of the polymer 120away from the preform structure 16.

The method for making the OLED 40 as shown in FIG. 26 is similar to themethod for making the carbon nanotube composite structure 180 as shownin FIG. 12 above except that: 1) in FIG. 12, the carbon nanotubestructure 110 is placed on the substrate 100; in FIG. 26, the carbonnanotube structure 110 is placed on the preform structure 16; 2) in FIG.12, both the substrate 100 and the container 182 are removed; in FIG.26, only the container 182 is removed, and the cathode electrode 15 isformed on the polymer 120.

Referring to FIG. 27, another method for making the OLED 40 of theeighth embodiment includes the following steps:

S81′, providing the preform structure 16 including the support body 11,the anode electrode 12, the hole transport layer 13, and the organiclight emitting layer 14, wherein the support body 11, the anodeelectrode 12, the hole transport layer 13, and the organic lightemitting layer 14 are stacked on each other in that order;

S82′, placing the carbon nanotube composite structure 180 on the surfaceof the organic light emitting layer 14 away from the hole transportlayer 13, wherein carbon nanotube composite structure 180 includes theplurality of first carbon nanotubes 1180, the plurality of second carbonnanotubes 1182, and the plurality of carbon nanotubes 1184; the part ofthe surface of each first carbon nanotube 1180 is exposed from thepolymer 120 and in direct contact with the organic light emitting layer14, and the part of the surface of each second carbon nanotube 1182 isexposed from the polymer 120; and entire surface of the plurality ofcarbon nanotubes is covered by the polymer 120; and

S83′, forming the cathode electrode 15 on the surface of the carbonnanotube composite structure 180 away from the organic light emittinglayer 14, wherein the part of the surface of each second carbon nanotube1182 is exposed from the polymer 120 and in direct contact with thecathode electrode 15.

The method as shown in FIG. 27 is similar to the method as shown in FIG.19 above except that the carbon nanotube composite structure isdifferent in the two methods.

Yet another method for making the OLED 40 of the eighth embodimentincludes the following steps:

S81″, providing the carbon nanotube composite structure 180;

S82″, forming the cathode electrode 15 on the carbon nanotube compositestructure 180; and

S83″, forming the preform structure 16 on the surface of the carbonnanotube composite structure 180 away from the cathode electrode 15,wherein the organic light emitting layer 14 is in direct contact withthe carbon nanotube composite structure 180.

Referring to FIG. 28, an OLED 50 of a ninth embodiment is shown. TheOLED 50 is similar to the OLED 40 above except that a part of thesurface of each first carbon nanotube 1180 is exposed from the polymer120 and in direct contact with the cathode electrode 15, a part of thesurface of each second carbon nanotube 1182 is exposed from the polymer120 and in direct contact with the organic light emitting layer 14, andeach second carbon nanotube 1182 is embedded in the organic lightemitting layer 14.

Referring to FIG. 29, a method for making the OLED 50 of the ninthembodiment includes the following steps:

S91, placing the carbon nanotube structure 110 on the cathode electrode15;

S92, placing the carbon nanotube structure 110 and the cathode electrode15 into the container 182, wherein the container 182 has the opening;

S93, injecting the monomer solution 140 into the container 182 from theopening of the container 182, wherein the monomer solution 140 is formedby dispersing the monomer into the organic solvent;

S94, polymerizing the monomer to form the polymer 120;

S95, removing the container 182; and

S96, placing the preform structure 16 on the surface of the polymer 120away from the cathode electrode 15, wherein the organic light emittinglayer 14 is in direct contact with the polymer 120.

The method for making the OLED 50 as shown in FIG. 29 is similar to themethod for making the carbon nanotube composite structure 180 as shownin FIG. 12 above except that: 1) in FIG. 12, the carbon nanotubestructure 110 is placed on the substrate 100; in FIG. 29, the carbonnanotube structure 110 is placed on the cathode electrode 15; 2) in FIG.12, both the substrate 100 and the container 182 are removed; in FIG.29, only the container 182 is removed, and the preform structure 16 isplaced on the polymer 120. In this embodiment, the cathode electrode 15is an aluminum plate.

The methods shown in FIGS. 14, 18, 23, 26, and 29 have some advantagesbelow. The preform structure 16 or the cathode electrode 15 is used as asubstrate for supporting the carbon nanotube structure 110. The monomersolution 140 is coated on the carbon nanotube structure 110, then themonomer of the monomer solution 140 is polymerized to form the electrontransport layer, and then other functional layers are set. The monomersolution 140 has a low viscosity, thus the monomer solution 140 can beuniformly distributed in the carbon nanotube structure 110. Afterpolymerizing the monomer, the carbon nanotubes 118 have good dispersionin the electron transport layer, thereby the transmitting electronsability of the electron transport layer is improved.

Referring to FIG. 30, another method for making the OLED 50 of the ninthembodiment includes the following steps:

S91′, placing the carbon nanotube composite structure 180 on the cathodeelectrode 15, wherein in the carbon nanotube composite structure 180,the part of the surface of each first carbon nanotube 1180 is exposedfrom the polymer 120 and in direct contact with the cathode electrode15, the part of the surface of each second carbon nanotube 1182 isexposed from the polymer 120, and entire surface of the plurality ofcarbon nanotubes is covered by the polymer 120;

S92′, forming the organic light emitting layer 14 on the surface of thecarbon nanotube composite structure 180 away from the cathode electrode15; and

S93′, forming the hole transport layer 13 on the surface of the organiclight emitting layer 14 away from the carbon nanotube compositestructure 180;

S94′, forming the anode electrode 12 on the surface of the holetransport layer 13 away from the organic light emitting layer 14; and

S95′, placing the support body 11 on the surface of the anode electrode12 away from the hole transport layer 13.

In the step S91′, the cathode electrode 15 can support other element,and the material of the cathode electrode 15 is not limited. In oneembodiment, the cathode electrode 15 is the aluminum plate. In the stepsS92′ and S93′, the organic light emitting layer 14, the hole transportlayer 13, and the anode electrode 12 are formed by sputtering, coating,vapor deposition, mask etching, spraying, or inkjet printing. The stepS95′ can be omitted.

The methods shown in FIGS. 15, 19, 24, 27, and 30 have some advantagesbelow. The support body 11, the anode electrode 12, the hole transportlayer 13, the organic light emitting layer 14, and the carbon nanotubecomposite structure 130 (170 or 180) are successively laminatedtogether. Then, the organic light emitting layer 14 and the carbonnanotube composite structure 130 (170 or 180) are tightly bonded bypressing. Finally, the cathode electrode 15 is formed on the surface ofthe carbon nanotube composite structure 130 (170 or 180) away from theorganic light emitting layer 14. The carbon nanotubes 118 of the carbonnanotube composite structure 130 (170 or 180) are substantially parallelto each other and extend the same direction. The relatively regulararrangement of the carbon nanotubes 118 can improve the transmittingelectrons ability of the electron transport layer.

Referring to FIG. 31, an OLED 60 of a tenth embodiment is shown. TheOLED 60 is similar to the OLED 10. The difference between the OLED 10and the OLED 60 is that the electron transport layer of the OLED 10 isthe carbon nanotube composite structure 130, however the electrontransport layer of the OLED 60 is a carbon nanotube compositesub-structure 131 which is formed by treating the carbon nanotubecomposite structure 130.

In the OLED 60, the carbon nanotube composite sub-structure 131 includesthe polymer 120 and a plurality of carbon nanotubes 118 dispersed in thepolymer 120. The length direction of the plurality of carbon nanotubes118 is from the organic light emitting layer 14 to the cathode electrode15. In OLED 60, each carbon nanotube 118 has a first end and a secondend opposite to the first end, the first end is exposed from the polymer120 and in direct contact with the organic light emitting layer 14, andthe second end is exposed from the polymer 120 and in direct contactwith the cathode electrode 15. The plurality of carbon nanotubes 118 areparallel to each other. The material of the polymer 120 in the carbonnanotube composite sub-structure 131 is not limited. The carbon nanotubecomposite sub-structure 131 has a first sub-structure surface 137 thatis in direct contact with the organic light emitting layer 14. Thelength direction of the plurality of carbon nanotubes 118 and thesub-structure surface form an angle, and the angle is grater than 0degrees and less than or equal to 90 degrees. In one embodiment, thelength direction of the plurality of carbon nanotubes 118 isperpendicular to the sub-structure surface.

Referring to FIG. 33, a method for making the OLED 60 of the tenthembodiment includes the following steps:

S101, providing the preform structure 16 including the support body 11,the anode electrode 12, the hole transport layer 13, and the organiclight emitting layer 14, wherein the support body 11, the anodeelectrode 12, the hole transport layer 13, and the organic lightemitting layer 14 are stacked on each other in that order;

S102, treating the carbon nanotube composite structure 130 to form thecarbon nanotube composite sub-structure 131 having the sub-structuresurface and the plurality of carbon nanotubes 118, wherein the lengthdirection of the plurality of carbon nanotubes 118 is parallel to thethickness direction of the carbon nanotube composite sub-structure 131;

S103, placing the carbon nanotube composite sub-structure 131 on thepreform structure 16, wherein the carbon nanotube compositesub-structure 131 is in direct contact with the organic light emittinglayer 14; and

S104, forming the cathode electrode 15 on the surface of the carbonnanotube composite sub-structure 131 away from the preform structure 16.

The step S102 can be performed before the step S101.

In the step 102, the thickness of the carbon nanotube compositestructure 130 in this embodiment is greater than the thickness of thecarbon nanotube composite structure 130 in the first embodiment. Theamount of the monomer solution 140 can be increased so that thethickness of the polymer 120 becomes large, thus the thickness of thecarbon nanotube composite structure 130 becomes large.

The carbon nanotube composite structure 130 is treated by slicing. Thecarbon nanotube composite structure 130 is cut by laser along adirection perpendicular to the first composite structure surface 132, asshown in FIG. 32. The carbon nanotube composite structure 130 has athird composite structure surface 134 and a fourth composite structuresurface 136 opposite to the third composite structure surface 134. Inone embodiment, the third composite structure surface 134 and the fourthcomposite structure surface 136 are perpendicular to the first compositestructure surface 132. When the carbon nanotube composite structure 130is cut, a cut line AB is formed on the carbon nanotube compositestructure 130. The cut line AB can be perpendicular to the lengthdirection of the carbon nanotubes 118 and parallel to the thirdcomposite structure surface 134. The distance between the cut line ABand the third composite structure surface 134 can be adjusted, and thecarbon nanotube composite sub-structure 131 is formed after cuttingalong the cut line AB. The carbon nanotube composite sub-structure 131is a sheet or a film. The carbon nanotube composite sub-structure 131has the first sub-structure surface 137 and a second sub-structuresurface 138 opposite to the first sub-structure surface 137. The firstsub-structure surface 137 is parallel to the third composite structuresurface 134, and the second sub-structure surface 138 is parallel to thefourth composite structure surface 136. In one embodiment, the lengthdirection of each carbon nanotube 118 is perpendicular to the thirdcomposite structure surface 134.

The carbon nanotube composite sub-structure 131 can conduct andtransport electrons, so the cathode electrode 15 can be omitted, and thestep S104 can be omitted.

Referring to FIG. 34, another method for making the OLED 60 of the tenthembodiment includes the following steps:

S101′, treating the carbon nanotube composite structure 130 to form thecarbon nanotube composite sub-structure 131 having the firstsub-structure surface 137, the second sub-structure surface 138 and theplurality of carbon nanotubes 118, wherein the length direction of theplurality of carbon nanotubes 118 is parallel to the thickness directionof the carbon nanotube composite sub-structure 131;

S102′, placing the carbon nanotube composite sub-structure 131 on thecathode electrode 15, and the second sub-structure surface 138 is indirect contact with the cathode electrode 15;

S103′, placing the preform structure 16 on the first sub-structuresurface 137, wherein the carbon nanotube composite sub-structure 131 isin direct contact with the organic light emitting layer 14.

The OLED 60 shown in FIG. 31 and the methods shown in FIG. 33 and FIG.34 have some advantages below. The electrical conductivity of the carbonnanotube 118 along the longitudinal direction (axial direction) is good,and the electrical conductivity of the carbon nanotube 118 along theradial direction is poor. The length direction of the plurality ofcarbon nanotubes 118 is from the organic light emitting layer 14 to thecathode electrode 15, thus transmitting electrons ability of theelectron transport layer is improved. In addition, both the polymerhaving transmitting electrons ability and the polymer withouttransmitting electrons can be materials of the polymer 120.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size and arrangement of the parts within theprinciples of the present disclosure up to, and including, the fullextent established by the broad general meaning of the terms used in theclaims.

Additionally, it is also to be understood that the above description andthe claims drawn to a method may comprise some indication in referenceto certain steps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A method for making an organic light emittingdiode, the method comprising: providing a preform structure comprisingan anode electrode, a hole transport layer, and an organic lightemitting layer stacked on each other in that order, wherein the organiclight emitting layer has a first surface and a second surface oppositeto the first surface, and the second surface is in direct contact withthe hole transport layer; placing a carbon nanotube structure comprisinga plurality of carbon nanotubes on the first surface; disposing amonomer solution on the carbon nanotube structure after placing thecarbon nanotube structure on the first surface, wherein the monomersolution is formed by dispersing a monomer into an organic solvent;polymerizing the monomer to form a polymer; and forming a cathodeelectrode on a surface of the polymer away from the preform structure.2. The method of claim 1, wherein the preform structure furthercomprises a support body for supporting the anode electrode, the holetransport layer, and the organic light emitting layer.
 3. The method ofclaim 1, wherein the plurality of carbon nanotubes is joined end-to-endby van der Wards attractive force and extends substantially along thesame direction.
 4. The method of claim 1, wherein the plurality ofcarbon nanotubes is substantially parallel to the first surface.
 5. Themethod of claim 1, wherein a plurality of gaps is defined by theplurality of carbon nanotubes, and the monomer solution passes throughthe plurality of gaps and arrive at the first surface during disposingthe monomer solution.
 6. The method of claim 1, wherein the polymer hasan ability to transmit electrons.
 7. The method of claim 1, wherein thedisposing the monomer solution comprises placing the carbon nanotubestructure and the preform structure in a container and injecting themonomer solution to the container.
 8. The method of claim 3, wherein thecarbon nanotube structure comprises two carbon nanotube films, and anangle between the plurality of first carbon nanotubes in the two carbonnanotube films ranges from about 0 degree to about 90 degrees.
 9. Amethod for making an organic light emitting diode, the methodcomprising: providing a preform structure comprising an anode electrode,a hole transport layer, and an organic light emitting layer stacked oneach other in that order, wherein the organic light emitting layer has afirst surface and a second surface opposite to the first surface, andthe second surface is indirect contact with the hole transport layer;placing a first carbon nanotube structure comprising a plurality offirst carbon nanotubes on the first surface to form a first compositestructure; placing a second carbon nanotube structure comprising aplurality of second carbon nanotubes on a surface of a cathode electrodeto form a second composite structure; locating the first compositestructure and the second composite structure on a base, wherein thebase, the preform structure, and the cathode electrode form a moldhaving an opening, the first composite structure and the secondcomposite structure are spaced apart from each other; and the firstcarbon nanotube structure and the second carbon nanotube structure areopposite to each other and inside of the mold; injecting the monomersolution into the inside of the mold from the opening, wherein themonomer solution is formed by dispersing a monomer into an organicsolvent; polymerizing the monomer; and removing the base.
 10. The methodof claim 9, wherein the plurality of first carbon nanotubes is joinedend-to-end by van der Waals attractive force, and substantially extendsalong the same direction.
 11. The method of claim 9, wherein theplurality of second carbon nanotubes is joined end-to-end by van derWaals attractive force and substantially extends along the samedirection.
 12. The method of claim 9, wherein the plurality of firstcarbon nanotubes is substantially parallel to the first surface.
 13. Themethod of claim 9, wherein the plurality of second carbon nanotubes issubstantially parallel to the surface of the cathode electrode.
 14. Themethod of claim 9, wherein a plurality of first gaps is defined by theplurality of first carbon nanotubes, and the monomer solution passesthrough the plurality of first gaps and arrive at the first surfaceduring injecting the monomer solution.
 15. The method of claim 9,wherein a plurality of second gaps is defined by the plurality of secondcarbon nanotubes, and the monomer solution passes through the pluralityof second gaps and arrive at the surface of the cathode electrode duringinjecting the monomer solution.
 16. The method of claim 9, wherein thepolymer has ara ability to transmit electrons.